326 Herre 



the study of lichens as easy as that of the Liverworts, Grasses, 

 Compositas, or other more difficult groups. 



The Santa Cruz peninsula comprises that region lying west 

 of San Francisco Bay and the broad, originally treeless Santa 

 Clara valley, and north of Monterey Bay, and forms a natural 

 biological region. In it are included the counties of San Fran- 

 cisco, San Mateo, Santa Cruz and a part of Santa Clara. It 

 rises from sea level on three sides to 3788 feet on Loma Prieta, 

 the highest of the Santa Cruz mountains. The Pacific side of 

 the peninsula is very moist and in the fog-laden air of the red- 

 wood or forest formation certain forms of lichens reach a devel- 

 opment perhaps unsurpassed elsewhere. 



In studying the lichens of this region special attention has 

 been paid to their distribution as it is believed that the presence 

 or absence of lichens is an ecological factor of quite as much 

 moment as the presence or absence of any other plants. To 

 say that lichens are irresponsive to conditions of temperature, 

 light, and moisture, and that they are of no importance in study- 

 ing plant ecology, is a gross fallacy. 



Not all the Santa Cruz peninsula has been explored for 

 lichens, but practically every portion has been visited except the 

 region of the Big Basin. It is believed that the plants described 

 in this paper include a large majority of the forms which are 

 indigenous to this region. 



It is now nearly forty years since Bolander collected about 

 San Francisco. His lichens were determined by Tuckerman, 

 a great many being described then for the first time. Since 

 Bolander ceased his work, Dr. Marshall A. Howe collected 

 three or four forms in San Mateo county, which were distributed 

 in the published exsiccata of Cummings, Seymour, and Wil- 

 liams. C. F. Baker also collected a score or less of the com- 

 monest lichens about Stanford University, the determinations 

 being made by Dr. H. E. Hasse. 



Aside from these no collecting has been done in this region, 

 and there is no doubt tnat careful search will reveal many 

 new forms. Already several new lichens have been found by 

 the author although the crustaceous lichens have hardly been 

 noticed or collected. 



